15-Hydroxyprostaglandin dehydrogenase generation of electrophilic lipid signaling mediators from hydroxy ω-3 fatty acids

Lipoxin A4 yields an electrophilic 15-oxo metabolite that mediates FPR2 receptor-independent anti-inflammatory signaling

The enzymatic oxidation of arachidonic acid is proposed to yield trihydroxytetraene species (termed lipoxins) that resolve inflammation via ligand activation of the formyl peptide receptor, FPR2. While cell and murine models activate signaling responses to synthetic lipoxins, primarily 5S,6R,15S-trihydroxy-7E,9E,11Z,13E-eicosatetraenoic acid (lipoxin A4, LXA4), there are expanding concerns about the biological formation, detection and signaling mechanisms ascribed to LXA4 and related di- and tri-hydroxy ω-6 and ω-3 fatty acids. Herein, the generation and actions of LXA4 and its primary 15-oxo metabolite were assessed in control, LPS-activated and arachidonic acid supplemented RAW 264.7 macrophages. Despite protein expression of all enzymes required for LXA4 synthesis, both LXA4 and its 15-oxo-LXA4 metabolite were undetectable. Moreover, synthetic LXA4 and the membrane permeable 15-oxo-LXA4 methyl ester that is rapidly de-esterified to 15-oxo-LXA4, displayed no ligand activity for the putative LXA4 receptor FPR2, as opposed to the FPR2 ligand WKYMVm. Alternatively, 15-oxo-LXA4, an electrophilic α,β-unsaturated ketone, alkylates nucleophilic amino acids such as cysteine to modulate redox-sensitive transcriptional regulatory protein and enzyme function. 15-oxo-LXA4 activated nuclear factor (erythroid related factor 2)-like 2 (Nrf2)-regulated gene expression of anti-inflammatory and repair genes and inhibited nuclear factor (NF)-κB-regulated pro-inflammatory mediator expression. LXA4 did not impact these macrophage anti-inflammatory and repair responses. In summary, these data show an absence of macrophage LXA4 formation and receptor-mediated signaling actions. Rather, if LXA4 were present in sufficient concentrations, this, and other more abundant mono- and poly-hydroxylated unsaturated fatty acids can be readily oxidized to electrophilic α,β-unsaturated ketone products that modulate the redox-sensitive cysteine proteome via G-protein coupled receptor-independent mechanisms.

Impact of Reperfusion on Plasma Oxylipins in ST-Segment Elevation Myocardial Infarction

ST-segment elevation myocardial infarction (STEMI) occurs as a result of acute occlusion of the coronary artery. Despite successful reperfusion using primary percutaneous coronary intervention (PPCI), a large percentage of myocardial cells die after reperfusion, which is recognized as ischemia/reperfusion injury (I/R). There are rapid changes in plasma lipidome during myocardial reperfusion injury. However, the impact of coronary artery reperfusion on plasma oxylipins is unknown. This study aimed to investigate alterations in the oxylipin profiles of STEMI patients during ischemia and at various reperfusion time points following PPCI. Blood samples were collected from patients presenting with STEMI prior to PPCI (Isch, n = 45) and subsequently 2 h following successful reperfusion by PPCI (R-2 h, n = 42), after 24 h (R-24 h, n = 44), after 48 h (R-48 h, n = 43), and then 30 days post PPCI (R-30 d, n = 29). As controls, blood samples were collected from age- and sex-matched patients with non-obstructive coronary artery disease after diagnostic coronary angiography. High-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) using deuterated standards was used to identify and quantify oxylipins. In patients presenting with STEMI prior to reperfusion (Isch group), the levels of docosahexaenoic acid (DHA)-derived oxylipins were significantly higher when compared with controls. Their levels were also significantly correlated with the peak levels of creatine kinase (CK) and troponin T(TnT) before reperfusion (CK: r = 0.33, p = 0.046, TnT: r = 0.50, p = 1.00 × 10-3). The total concentrations of oxylipins directly produced by 5-lipoxygenase (5-LOX) were also significantly elevated in the Isch group compared with controls. The ratio of epoxides (generated through epoxygenase) to diols (generated by soluble epoxide hydrolysis (sEH)) was significantly lower in the Isch group compared with the controls. Following reperfusion, there was an overall reduction in plasma oxylipins in STEMI patients starting at 24 h post PPCI until 30 days. Univariate receiver operating characteristic (ROC) curve analysis also showed that an elevated ratio of epoxides to diols during ischemia is a predictor of smaller infarct size in patients with STEMI. This study revealed a large alteration in plasma oxylipins in patients presenting with STEMI when compared with controls. Total oxylipin levels rapidly reduced post reperfusion with stable levels reached 24 h post reperfusion and maintained for up to 30 days post infarct. Given the shifts in plasma oxylipins following coronary artery reperfusion, further research is needed to delineate their clinical impact in STEMI patients.

Protection of Inonotus hispidus (Bull.) P. Karst. against Chronic Alcohol-Induced Liver Injury in Mice via Its Relieving Inflammation Response

Alcoholic liver disease (ALD) can be induced by excessive alcohol consumption, and has a worldwide age-standardized incidence rate (ASIR) of approximately 5.243%. Inonotus hispidus (Bull.) P. Karst. (IH) is a mushroom with pharmacological effects. In ALD mice, the hepatoprotective effects of IH were investigated. IH strongly ameliorated alcohol-induced pathological changes in the liver, including liver structures and its function-related indices. Intestinal microbiota and serum metabolomics analysis showed that IH altered the associated anti-inflammatory microbiota and metabolites. According to results obtained from Western blot, immunohistochemistry (IHC), and enzyme-linked immunosorbent assay (ELISA), IH downregulated the levels of pro-inflammation factors interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α), enhanced the expressions of peroxisome proliferator-activated receptor alpha (PPARα) and 15-hydroxprostaglandin dehydrogenase (15-PGDH), and inhibited the phosphorylated activation of Janus kinase (JAK) 1 and signal transducer and activator of transcription (STAT) 3, confirming the hepatoprotection of IH against alcohol damage via anti-inflammation. This study provides the experimental evidence for the hepatoprotective effects of IH in chronic ALD.

4-Methylumbelliferone Targets Revealed by Public Data Analysis and Liver Transcriptome Sequencing

4-methylumbelliferone (4MU) is a well-known hyaluronic acid synthesis inhibitor and an approved drug for the treatment of cholestasis. In animal models, 4MU decreases inflammation, reduces fibrosis, and lowers body weight, serum cholesterol, and insulin resistance. It also inhibits tumor progression and metastasis. The broad spectrum of effects suggests multiple and yet unknown targets of 4MU. Aiming at 4MU target deconvolution, we have analyzed publicly available data bases, including: 1. Small molecule library Bio Assay screening (PubChemBioAssay); 2. GO pathway databases screening; 3. Protein Atlas Database. We also performed comparative liver transcriptome analysis of mice on normal diet and mice fed with 4MU for two weeks. Potential targets of 4MU public data base analysis fall into two big groups, enzymes and transcription factors (TFs), including 13 members of the nuclear receptor superfamily regulating lipid and carbohydrate metabolism. Transcriptome analysis revealed changes in the expression of genes involved in bile acid metabolism, gluconeogenesis, and immune response. It was found that 4MU feeding decreased the accumulation of the glycogen granules in the liver. Thus, 4MU has multiple targets and can regulate cell metabolism by modulating signaling via nuclear receptors.

Polyunsaturated fatty acids and fatty acid-derived lipid mediators: Recent advances in the understanding of their biosynthesis, structures, and functions

Polyunsaturated fatty acids (PUFAs) are structural components of membrane phospholipids, and influence cellular function via effects on membrane properties, and also by acting as a precursor pool for lipid mediators. These lipid mediators are formed via activation of pathways involving at least one step of dioxygen-dependent oxidation, and are consequently called oxylipins. Their biosynthesis can be either enzymatically-dependent, utilising the promiscuous cyclooxygenase, lipoxygenase, or cytochrome P450 mixed function oxidase pathways, or nonenzymatic via free radical-catalyzed pathways. The oxylipins include the classical eicosanoids, comprising prostaglandins, thromboxanes, and leukotrienes, and also more recently identified lipid mediators. With the advent of new technologies there is growing interest in identifying these different lipid mediators and characterising their roles in health and disease. This review brings together contributions from some of those at the forefront of research into lipid mediators, who provide brief introductions and summaries of current understanding of the structure and functions of the main classes of nonclassical oxylipins. The topics covered include omega-3 and omega-6 PUFA biosynthesis pathways, focusing on the roles of the different fatty acid desaturase enzymes, oxidized linoleic acid metabolites, omega-3 PUFA-derived specialized pro-resolving mediators, elovanoids, nonenzymatically oxidized PUFAs, and fatty acid esters of hydroxy fatty acids.

MiR-106b-5p regulates esophageal squamous cell carcinoma progression by binding to HPGD

BACKGROUND

Several studies have documented the key role of microRNAs (miRNAs) in esophageal squamous cell carcinoma (ESCC). Although the expression of the 15-hydroxyprostaglandin dehydrogenase (HPGD) gene and miR-106b-5p are reportedly linked to cancer progression, their underlying mechanisms in ESCC remain unclear.

METHODS

mRNA and miRNA expression in ESCC tissues and cells were analyzed using RT-qPCR. Luciferase and RNA pull-down assays were used to identify the interaction between miR-106b-5p and HPGD. Xenograft and pulmonary metastasis models were used to assess tumor growth and metastasis. CCK-8, BrdU, colony formation, adhesion, cell wound healing, Transwell, and caspase-3/7 activity assays, and flow cytometry and western blot analyses were used to examine the function of miR-106-5p and HPGD in ESCC cell lines.

RESULTS

The findings revealed that miR-106b-5p expression was upregulated in ESCC tissues and cell lines. miR-106b-5p augmented cellular proliferation, colony formation, adhesion, migration, invasion, and proportion of cells in the S-phase, but reduced apoptosis and the proportion of cells in G1-phase. Silencing of miR-106-5p inhibited tumor growth in vivo and pulmonary metastasis. Although HPGD overexpression suppressed proliferation, colony formation, adhesion, migration, and invasion of ESCC cells, it promoted apoptosis and caused cell cycle arrest of the ESCC cells. The results also indicated a direct interaction of HPGD with miR-106b-5p in ESCC cells. Furthermore, miR-106b-5p inhibited HPGD expression, thereby suppressing ESCC tumorigenesis.

CONCLUSION

Our data suggest that miR-106b-5p enhances proliferation, colony formation, adhesion, migration, and invasion, and induces the cycle progression, but represses apoptosis of ESCC cells by targeting HPGD. This suggests that the miR-106b-5p/HPGD axis may serve as a promising target for the diagnosis and treatment of ESCC.

Oxylipin metabolism is controlled by mitochondrial β-oxidation during bacterial inflammation

Oxylipins are potent biological mediators requiring strict control, but how they are removed en masse during infection and inflammation is unknown. Here we show that lipopolysaccharide (LPS) dynamically enhances oxylipin removal via mitochondrial β-oxidation. Specifically, genetic or pharmacological targeting of carnitine palmitoyl transferase 1 (CPT1), a mitochondrial importer of fatty acids, reveal that many oxylipins are removed by this protein during inflammation in vitro and in vivo. Using stable isotope-tracing lipidomics, we find secretion-reuptake recycling for 12-HETE and its intermediate metabolites. Meanwhile, oxylipin β-oxidation is uncoupled from oxidative phosphorylation, thus not contributing to energy generation. Testing for genetic control checkpoints, transcriptional interrogation of human neonatal sepsis finds upregulation of many genes involved in mitochondrial removal of long-chain fatty acyls, such as ACSL1,3,4, ACADVL, CPT1B, CPT2 and HADHB. Also, ACSL1/Acsl1 upregulation is consistently observed following the treatment of human/murine macrophages with LPS and IFN-γ. Last, dampening oxylipin levels by β-oxidation is suggested to impact on their regulation of leukocyte functions. In summary, we propose mitochondrial β-oxidation as a regulatory metabolic checkpoint for oxylipins during inflammation.

Primary saturation of α, β-unsaturated carbonyl containing fatty acids does not abolish electrophilicity

Metabolism of polyunsaturated fatty acids results in the formation of hydroxylated fatty acids that can be further oxidized by dehydrogenases, often resulting in the formation of electrophilic, α,β-unsaturated ketone containing fatty acids. As electrophiles are associated with redox signaling, we sought to investigate the metabolism of the oxo-fatty acid products in relation to their double bond architecture. Using an untargeted liquid chromatography mass spectrometry approach, we identified mono- and di-saturated products of the arachidonic acid-derived 11-oxoeicosatetraenoic acid (11-oxoETE) and mono-saturated metabolites of 15-oxoETE and docosahexaenoic acid-derived 17-oxodocosahexaenoinc acid (17-oxoDHA) in both human A549 lung carcinoma and umbilical vein endothelial cells. Notably, mono-saturated oxo-fatty acids maintained their electrophilicity as determined by nucleophilic conjugation to glutathione while a second saturation of 11-oxoETE resulted in a loss of electrophilicity. These results would suggest that prostaglandin reductase 1 (PTGR1), known only for its reduction of the α,β-unsaturated double bond, was not responsible for the saturation of oxo-fatty acids at alternative double bonds. Surprisingly, knockdown of PTGR1 expression by shRNA confirmed its participation in the formation of 15-oxoETE and 17-oxoDHA mono-saturated metabolites. Furthermore, overexpression of PTGR1 in A549 cells increased the rate and total amount of oxo-fatty acid saturation. These findings will further facilitate the study of electrophilic fatty acid metabolism and signaling in the context of inflammatory diseases and cancer where they have been shown to have anti-inflammatory and anti-proliferative signaling properties.

12/15-Lipoxygenase Regulates IL-33-Induced Eosinophilic Airway Inflammation in Mice

Dysregulated fatty acid metabolism is clinically associated with eosinophilic allergic diseases, including severe asthma and chronic rhinosinusitis. This study aimed to demonstrate the role of 12/15-lipoxygenase (12/15-LOX) in interleukin (IL)-33-induced eosinophilic airway inflammation; to this end, we used 12/15-LOX-deficient mice, which displayed augmented IL-33-induced lung inflammation, characterized by an increased number of infiltrated eosinophils and group 2 innate lymphoid cells (ILC2s) in the airway. Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based lipidomics revealed that the levels of a series of 12/15-LOX-derived metabolites were significantly decreased, and application of 14(S)-hydroxy docosahexaenoic acid (HDoHE), a major 12/15-LOX-derived product, suppressed IL-33-mediated eosinophilic inflammation in 12/15-LOX-deficient mice. Using bioactive lipid screening, we found that 14(S)-HDoHE and 10(S),17(S)-diHDoHE markedly attenuated ILC2 proliferation and cytokine production at micromolar concentration in vitro. In addition, maresin 1 (MaR1) and resolvin D1 (RvD1), 12/15-LOX-derived specialized proresolving mediators (SPMs), inhibited cytokine production of ILC2s at nanomolar concentration. These findings demonstrate the protective role of endogenous 12/15-LOX-derived lipid mediators in controlling ILC2-mediated eosinophilic airway inflammation and related diseases. Thus, 12/15-LOX-derived lipid mediators may represent a potential therapeutic strategy for ameliorating airway inflammation-associated conditions.

Electrophile Modulation of Inflammation: A Two-Hit Approach

Electrophilic small molecules have gained significant attention over the last decade in the field of covalent drug discovery. Long recognized as mediators of the inflammatory process, recent evidence suggests that electrophiles may modulate the immune response through the regulation of metabolic networks. These molecules function as pleiotropic signaling mediators capable of reversibly reacting with nucleophilic biomolecules, most notably at reactive cysteines. More specifically, electrophiles target critical cysteines in redox regulatory proteins to activate protective pathways such as the nuclear factor erythroid 2-related factor 2-Kelch-like ECH-associated protein 1 (Nrf2-Keap1) antioxidant signaling pathway while also inhibiting Nuclear Factor κB (NF-κB). During inflammatory states, reactive species broadly alter cell signaling through the oxidation of lipids, amino acids, and nucleic acids, effectively propagating the inflammatory sequence. Subsequent changes in metabolic signaling inform immune cell maturation and effector function. Therapeutic strategies targeting inflammatory pathologies leverage electrophilic drug compounds, in part, because of their documented effect on the redox balance of the cell. With mounting evidence demonstrating the link between redox signaling and metabolism, electrophiles represent ideal therapeutic candidates for the treatment of inflammatory conditions. Through their pleiotropic signaling activity, electrophiles may be used strategically to both directly and indirectly target immune cell metabolism.

Potential Biomarkers for Early Detection of 3-MCPD Dipalmitate Exposure in Sprague-Dawley Rats

3-Chloro-1,2-propandiol (3-MCPD) dipalmitate is one of the major 3-MCPD esters formed during food processing. In this single-dose study, the metabonomic profile changes in the 48 h after orally administrated 3-MCPD dipalmitate at 1600 mg/kg BW to Sprague-Dawley (SD) rats were determined with liquid chromatography (LC) coupled with mass spectrometry (MS) system. The chemical structures of 12 potential biomarkers for 3-MCPD dipalmitate exposures early detection were detected and tentatively identified from the plasma of SD rats, including indoxyl sulfate, phenol sulfate, p-cresol sulfate, 2-phenylethanol glucuronide, p-cresol glucuronide, p-cresol, allantoin, phenylacetylglycine, pyrocatechol sulfate, phenyllactic acid, 5-hydroxyindoleacetic acid, and creatinine. Taking into account the metabolites identified from SD rats' kidney, liver, testes, and spleen samples, 3-MCPD dipalmitate might potentially disturb the phenylalanine, tryptophan, tyrosine, glycine, fatty acid, and purine metabolisms. The results suggested that the 12 plasma metabolites could be potentially applied in detecting the early exposures of 3-MCPD esters.

Eicosapentaenoic acid's metabolism of 15-LOX-1 promotes the expression of miR-101 thus inhibits Cox2 pathway in colon cancer

Purpose

It is well known that diet Eicosapentaenoic acid (EPA) is beneficial to colon cancer (CC). However,  the underlying molecular mechanisms of EPA-relating miRNAs on genesis and development of this area is still unclear.

Materials and Methods

This study tries to find the function and specific role of EPA in CC through quantitative PCR (qPCR), Western blotting, immunofluorescence (IF), mass spectrometry, and immunohistochemistry (IHC) assays. By these methods, the enrichment of 15-LOX-1 metabolites of EPA, the expression of miR-101 and Cox2, and the relationship among them in CC are measured.

Results

The quantity of miR-101 was obviously suppressed in CC tissues and SW480 cells. After application of miR-101 mimics in CC cell lines, the Cox2 expression was inhibited too. Next, we confirmed that EPA could increase the expression of miR-101 induced by 15-LOX-1. Finally, we tested whether EPA functions as a regulator of miR-101 via the production of resolvin E3.

Conclusion

Our data demonstrate that the EPA–15-LOX-1–miR-101-Cox2 signaling pathway owns a crucial position in the pathogenesis and development of diet-related CC. These findings exert exciting meanings for presenting new therapeutic angles in CC.

Acute Hypercapnia/Ischemia Alters the Esterification of Arachidonic Acid and Docosahexaenoic Acid Epoxide Metabolites in Rat Brain Neutral Lipids

In the brain, approximately 90% of oxylipins are esterified to lipids. However, the significance of this esterification process is not known. In the present study, we (1) validated an aminopropyl solid phase extraction (SPE) method for separating esterified lipids using 100 and 500 mg columns and (2) applied the method to quantify the distribution of esterified oxylipins within phospholipids (PL) and neutral lipids (NL) (i.e. triacylglycerol and cholesteryl ester) in rats subjected to head-focused microwave fixation (controls) or CO2 -induced hypercapnia/ischemia. We hypothesized that oxylipin esterification into these lipid pools will be altered following CO2 -induced hypercapnia/ischemia. Lipids were extracted from control (n = 8) and CO2 -asphyxiated (n = 8) rat brains and separated on aminopropyl cartridges to yield PL and NL. The separated lipid fractions were hydrolyzed, purified with hydrophobic-lipophilic-balanced SPE columns, and analyzed with ultra-high-pressure liquid chromatography coupled to tandem mass spectrometry. Method validation showed that the 500 mg (vs 100 mg) aminopropyl columns yielded acceptable separation and recovery of esterified fatty acid epoxides but not other oxylipins. Two epoxides of arachidonic acid (ARA) were significantly increased, and three epoxides of docosahexaenoic acid (DHA) were significantly decreased in brain NL of CO2 -asphyxiated rats compared to controls subjected to head-focused microwave fixation. PL-bound fatty acid epoxides were highly variable and did not differ significantly between the groups. This study demonstrates that hypercapnia/ischemia alters the concentration of ARA and DHA epoxides within NL, reflecting an active turnover process regulating brain fatty acid epoxide concentrations.

Docosahexaenoic Acid Suppresses Silica-Induced Inflammasome Activation and IL-1 Cytokine Release by Interfering With Priming Signal

Occupational exposure to respirable crystalline silica (cSiO₂) has been etiologically linked to human autoimmunity. Intranasal instillation with cSiO₂ triggers profuse inflammation in the lung and onset of autoimmunity in lupus-prone mice; however, dietary supplementation with the omega-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) abrogates these responses. Inflammasome activation, IL-1 cytokine release, and death in alveolar macrophages following cSiO₂ exposure are early and critical events that likely contribute to triggering premature autoimmune pathogenesis by this particle. Here we tested the hypothesis that DHA suppresses cSiO₂-induced NLRP3 inflammasome activation, IL-1 cytokine release, and cell death in the macrophage. The model used was the murine macrophage RAW 264.7 cell line stably transfected with the inflammasome adapter protein ASC (RAW-ASC). Following priming with LPS, both the canonical activator nigericin and cSiO₂ elicited robust inflammasome activation in RAW-ASC cells, as reflected by IL-1β release and caspase-1 activation. These responses were greatly diminished or absent in wild-type RAW cells. In contrast to IL-1β, cSiO₂ induced IL-1α release in both RAW-ASC and to a lesser extent in RAW-WT cells after LPS priming. cSiO₂-driven effects in RAW-ASC cells were confirmed in bone-marrow derived macrophages. Pre-incubating RAW-ASC cells with 10 and 25 μM DHA for 24 h enriched this fatty acid in the phospholipids by 15- and 25-fold, respectively, at the expense of oleic acid. DHA pre-incubation suppressed inflammasome activation and release of IL-1β and IL-1α by nigericin, cSiO₂, and two other crystals - monosodium urate and alum. DHA's suppressive effects were linked to inhibition of LPS-induced Nlrp3, Il1b, and Il1a transcription, potentially through the activation of PPARγ. Finally, nigericin-induced death was inflammasome-dependent, indicative of pyroptosis, and could be inhibited by DHA pretreatment. In contrast, cSiO₂-induced death was inflammasome-independent and not inhibited by DHA. Taken together, these findings indicate that DHA suppresses cSiO₂-induced inflammasome activation and IL-1 cytokine release in macrophages by acting at the level of priming, but was not protective against cSiO₂-induced cell death.

Oxylipin profiling in endothelial cells in vitro - Effects of DHA and hydrocortisone upon an inflammatory challenge

Omega-3 poly-unsaturated fatty acids have been shown to have beneficial effects on several inflammatory-driven endpoints such as cardiovascular diseases. The anti-inflammatory effects of docosahexaenoic acid (DHA) are largely mediated through various oxylipins. Yet, mechanistic insights are limited. Here, we measured 53 oxylipins using LC-MS/MS in an in vitro model of endothelial cell inflammation, and compared the changes induced by DHA to hydrocortisone, a well-established anti-inflammatory drug. DHA modified several oxylipins derived from different precursors such as DHA, AA, LA and EPA. In response to a TNFα and IL-1-β challenge, DHA clearly reduced many COX-derived pro-inflammatory oxylipins, yet to a minor extent when compared to hydrocortisone. DHA also upregulated metabolites from the CYP and LOX pathways as opposed to hydrocortisone. Thus, DHA reduced pro-inflammation and enhanced pro-resolution, while hydrocortisone blunted both the pro- and anti-inflammatory pathways. Our results may fuel further research on the mitigation of corticosteroids adverse side-effects.

Morphological, transcriptional, and metabolic analyses of osmotic-adapted mechanisms of the halophilic Aspergillus montevidensis ZYD4 under hypersaline conditions

Halophilic fungi in hypersaline habitats require multiple cellular responses for high-salinity adaptation. However, the exact mechanisms behind these adaptation processes remain to be slightly known. The current study is aimed at elucidating the morphological, transcriptomic, and metabolomic changes of the halophilic fungus Aspergillus montevidensis ZYD4 under hypersaline conditions. Under these conditions, the fungus promoted conidia formation and suppressed cleistothecium development. Furthermore, the fungus differentially expressed genes (P < 0.0001) that controlled ion transport, amino acid transport and metabolism, soluble sugar accumulation, fatty acid β-oxidation, saturated fatty acid synthesis, electron transfer, and oxidative stress tolerance. Additionally, the hypersalinized mycelia widely accumulated metabolites, including amino acids, soluble sugars, saturated fatty acids, and other carbon- and nitrogen-containing compounds. The addition of metabolites-such as neohesperidin, biuret, aspartic acid, alanine, proline, and ornithine-significantly promoted the growth (P ≤ 0.05) and the morphological adaptations of A. montevidensis ZYD4 grown in hypersaline environments. Our study demonstrated that morphological shifts, ion equilibrium, carbon and nitrogen metabolism for solute accumulation, and energy production are vital to halophilic fungi so that they can build tolerance to high-salinity environments.

Brain oxylipin concentrations following hypercapnia/ischemia: effects of brain dissection and dissection time

PUFAs are precursors to bioactive oxylipin metabolites that increase in the brain following CO2-induced hypercapnia/ischemia. It is not known whether the brain-dissection process and its duration also alter these metabolites. We applied CO2 with or without head-focused microwave fixation for 2 min to evaluate the effects of CO2-induced asphyxiation, dissection, and dissection time on brain oxylipin concentrations. Compared with head-focused microwave fixation (control), CO2 followed by microwave fixation prior to dissection increased oxylipins derived from lipoxygenase (LOX), 15-hydroxyprostaglandin dehydrogenase (PGDH), cytochrome P450 (CYP), and soluble epoxide hydrolase (sEH) enzymatic pathways. This effect was enhanced when the duration of postmortem ischemia was prolonged by 6.4 min prior to microwave fixation. Brains dissected from rats subjected to CO2 without microwave fixation showed greater increases in LOX, PGDH, CYP and sEH metabolites compared with all other groups, as well as increased cyclooxygenase metabolites. In nonmicrowave-irradiated brains, sEH metabolites and one CYP metabolite correlated positively and negatively with dissection time, respectively. This study presents new evidence that the dissection process and its duration increase brain oxylipin concentrations, and that this is preventable by microwave fixation. When microwave fixation is not available, lipidomic studies should account for dissection time to reduce these artifacts.

A novel bioactive derivative of eicosapentaenoic acid (EPA) suppresses intestinal tumor development in ApcΔ14/+ mice

Familial adenomatous polyposis (FAP) is a genetic disorder characterized by the development of hundreds of polyps throughout the colon. Without prophylactic colectomy, most individuals with FAP develop colorectal cancer at an early age. Treatment with EPA in the free fatty acid form (EPA-FFA) has been shown to reduce polyp burden in FAP patients. Since high-purity EPA-FFA is subject to rapid oxidation, a stable form of EPA compound has been developed in the form of magnesium l-lysinate bis-eicosapentaenoate (TP-252). We assessed the chemopreventive efficacy of TP-252 on intestinal tumor formation using ApcΔ14/+ mice and compared it with EPA-FFA. TP-252 was supplemented in a modified AIN-93G diet at 1, 2 or 4% and EPA-FFA at 2.5% by weight and administered to mice for 11 weeks. We found that administration of TP-252 significantly reduced tumor number and size in the small intestine and colon in a dose-related manner and as effectively as EPA-FFA. To gain further insight into the cancer protection afforded to the colon, we performed a comprehensive lipidomic analysis of total fatty acid composition and eicosanoid metabolites. Treatment with TP-252 significantly decreased the levels of arachidonic acid (AA) and increased EPA concentrations within the colonic mucosa. Furthermore, a classification and regression tree (CART) analysis revealed that a subset of fatty acids, including EPA and docosahexaenoic acid (DHA), and their downstream metabolites, including PGE3 and 14-hydroxy-docosahexaenoic acid (HDoHE), were strongly associated with antineoplastic activity. These results indicate that TP-252 warrants further clinical development as a potential strategy for delaying colectomy in adolescent FAP patients.

Synthesis of an Electrophilic Keto-Tetraene 15-oxo-Lipoxin A4 Methyl Ester via a MIDA Boronate

15-oxo-Lipoxin A₄ (15-oxo- LXA₄) has been identified as a natural metabolite of the fatty acid signaling mediator Lipoxin A₄. Herein, we report a total synthesis of the methyl ester of 15-oxo-LXA₄ to be used in investigations of potential electrophilic bioactivity of this metabolite. The methyl ester of 15-oxo-LXA₄ was synthesized in a convergent 15 step (9 steps longest linear) sequence starting from 1-octyn-3-ol and 2-deoxy-D-ribose with Sonogashira and Suzuki cross-couplings of a MIDA boronate as key steps.

Anti-inflammatory effects of α-linolenic acid in M1-like macrophages are associated with enhanced production of oxylipins from α-linolenic and linoleic acid

Chronic inflammation, mediated in large part by proinflammatory macrophage populations, contributes directly to the induction and perpetuation of metabolic diseases, including obesity, insulin resistance and type 2 diabetes. Polyunsaturated fatty acids (PUFAs) can have profound effects on inflammation through the formation of bioactive oxygenated metabolites called oxylipins. The objective of this study was to determine if exposure to the dietary omega-3 PUFA α-linolenic acid (ALA) can dampen the inflammatory properties of classically activated (M1-like) macrophages derived from the human THP-1 cell line and to examine the accompanying alterations in oxylipin secretion. We find that ALA treatment leads to a reduction in lipopolysaccharide (LPS)-induced interleukin (IL)-1β, IL-6 and tumor necrosis factor-α production. Although ALA is known to be converted to longer-chain PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), DHA oxylipins were reduced overall by ALA treatment, as was LPS-induced secretion of EPA oxylipins. In contrast, we observed profound increases in oxylipins directly derived from ALA. Lipoxygenase products of linoleic acid were also dramatically increased, and LPS-induced production of AA oxylipins, particularly prostaglandin D2, was reduced. These results suggest that ALA may act to dampen the inflammatory phenotype of M1-like macrophages by a unique set of mechanisms distinct from those used by the long-chain omega-3 fatty acids EPA and DHA. Thus, there is strong rationale for investigating the functions of ALA oxylipins and lesser-known LA oxylipins since they hold promise as anti-inflammatory agents.

Electrophilic derivatives of omega-3 fatty acids counteract lung cancer cell growth

PURPOSE

17-oxo-DHA is an electrophilic keto-derivative of the omega-3 fatty acid docosahexaenoic acid (DHA) endogenously generated by cyclooxygenase-2 and a cellular dehydrogenase. 17-oxo-DHA displays anti-inflammatory and cytoprotective actions. DHA, alone or in combination with standard chemotherapy, displays antitumor activity. However, the effects of electrophilic keto-derivatives of DHA on cancer growth have never been evaluated. We investigated whether 17-oxo-DHA, alone or in combination with gemcitabine, displayed antitumor effects. Furthermore, we evaluated whether the enzyme 15-prostaglandin dehydrogenase (15-PGDH) was required for transducing the antitumor effects of DHA.

METHODS

A panel of five histologically different human non-small cell lung cancer (NSCLC) cell lines was used. Cells were treated with 17-oxo-DHA and gemcitabine, alone or in combination, and apoptosis, proliferation, Fas and FasL expression (mRNA and protein) and active caspase-3/7 and -8 were assessed. Furthermore, an inhibitor of 15-PGDH was used to test the involvement of this enzyme in mediating the antitumor effects of DHA.

RESULTS

17-oxo-DHA (50 µM, 72 h) significantly reduced proliferation, increased cell apoptosis, Fas and FasL expression as well as active caspase-8 and -3/7. When 17-oxo-DHA was given in combination with gemcitabine, stronger effects were observed compared to gemcitabine alone. The enzyme 15-PGDH was required for DHA to promote its full anti-apoptotic effect suggesting that enzymatically generated keto-derivatives of DHA mediate its antitumor actions.

CONCLUSIONS

Data herein provided, demonstrate that 17-oxo-DHA displays antitumor effects in NSCLC cell lines. Of note, the combination of 17-oxo-DHA plus gemcitabine, resulted in stronger anticancer effects compared to gemcitabine alone.

ROS-Mediated 15-Hydroxyprostaglandin Dehydrogenase Degradation via Cysteine Oxidation Promotes NAD+-Mediated Epithelial-Mesenchymal Transition

Nicotinamide adenine dinucleotide (NAD) levels decrease with aging as a result of aging-associated CD38 upregulation. Here, we established a cell model with decreased cellular NAD levels by overexpressing CD38 or treating cells with FK866, an inhibitor of nicotinamide phosphoribosyltransferase. We revealed that decreased NAD triggered reactive oxygen species (ROS)-mediated degradation of 15-hydroxyprostaglandin dehydrogenase (15-PGDH), which drove cells to undergo epithelial-mesenchymal transition (EMT). Moreover, we showed that oxidation of the Cys44 residue to sulfonic acid in 15-PGDH led to its degradation via non-canonical ubiquitination-proteasome and autophagy pathways. Mutation of Cys44 to alanine abolished ROS-induced 15-PGDH degradation. We demonstrated that 15-PGDH silencing promoted EMT, whereas supplementation with NAD precursors increased NAD and 15-PGDH stability, and reversed the EMT process. Taken together, these results suggest that declining NAD levels contribute to age-dependent increases in cancer incidence, and repletion of NAD precursors is beneficial for increasing 15-PGDH expression.

Bioactive metabolites of docosahexaenoic acid

Docosahexaenoic acid (DHA) is an essential fatty acid that is recognized as a beneficial dietary constituent and as a source of the anti-inflammatory specialized proresolving mediators (SPM): resolvins, protectins and maresins. Apart from SPMs, other metabolites of DHA also exert potent biological effects. This article summarizes current knowledge on the metabolic pathways involved in generation of DHA metabolites. Over 70 biologically active metabolites have been described, but are often discussed separately within specific research areas. This review follows DHA metabolism and attempts to integrate the diverse DHA metabolites emphasizing those with identified biological effects. DHA metabolites could be divided into DHA-derived SPMs, DHA epoxides, electrophilic oxo-derivatives (EFOX) of DHA, neuroprostanes, ethanolamines, acylglycerols, docosahexaenoyl amides of amino acids or neurotransmitters, and branched DHA esters of hydroxy fatty acids. These bioactive metabolites have pleiotropic effects that include augmenting energy expenditure, stimulating lipid catabolism, modulating the immune response, helping to resolve inflammation, and promoting wound healing and tissue regeneration. As a result they have been shown to exert many beneficial actions: neuroprotection, anti-hypertension, anti-hyperalgesia, anti-arrhythmia, anti-tumorigenesis etc. Given the chemical structure of DHA, the number and geometry of double bonds, and the panel of enzymes metabolizing DHA, it is also likely that novel bioactive derivatives will be identified in the future.

Endogenous Generation and Signaling Actions of Omega-3 Fatty Acid Electrophilic Derivatives

Dietary omega-3 polyunsaturated fatty acids (PUFAs) are beneficial for a number of conditions ranging from cardiovascular disease to chronic airways disorders, neurodegeneration, and cancer. Growing evidence has shown that bioactive oxygenated derivatives are responsible for transducing these salutary effects. Electrophilic oxo-derivatives of omega-3 PUFAs represent a class of oxidized derivatives that can be generated via enzymatic and nonenzymatic pathways. Inflammation and oxidative stress favor the formation of these signaling species to promote the resolution of inflammation within a fine autoregulatory loop. Endogenous generation of electrophilic oxo-derivatives of omega-3 PUFAs has been observed in in vitro and ex vivo human models and dietary supplementation of omega-3 PUFAs has been reported to increase their formation. Due to the presence of an α,β-unsaturated ketone moiety, these compounds covalently and reversibly react with nucleophilic residues on target proteins triggering the activation of cytoprotective pathways, including the Nrf2 antioxidant response, the heat shock response, and the peroxisome proliferator activated receptor γ (PPARγ) and suppressing the NF-κB proinflammatory pathway. The endogenous nature of electrophilic oxo-derivatives of omega-3 PUFAs combined with their ability to simultaneously activate multiple cytoprotective pathways has made these compounds attractive for the development of new therapies for the treatment of chronic disorders and acute events characterized by inflammation and oxidative stress.